Rob Portman, the director of the Office of Management and Budget, is resigning his post.

WASHINGTON (CNN) - Office of Management and Budget Director Rob Portman is resigning his post, CNN has learned from two administration officials.

Portman, a Republican who represented Ohio in the House before joining the Bush administration, will be replaced by another former House Republican, Jim Nussle of Iowa. Nussle served as the chairman of the House Budget Committee.

The president will make the announcement Tuesday at 2: 40 p.m. ET.

Republicans privately say this will be a blow to the White House with Portman leaving in the middle of major budget battles on Capitol Hill, especially since the White House has previously touted Portman’s close ties to Congressional Republican leaders as an important asset in the final 18 months of the Bush administration.

Two sources close to Portman also tell CNN that the former Republican congressman has about $1.5 million in old campaign funds and is moving back to Ohio to consider run for governor in 2010.

Nussle is currently on the staff of former New York City Mayor Rudy Giuliani's presidential campaign, serving as an Iowa advisor. Nussle lost a 2006 gubernatorial bid to Democrat Chet Culver by approximately 100,000 votes.